1. Field of the Invention
The present invention relates to oil based slurry compositions having decreased particulate material settling rates and to formulations including the oil based slurry compositions and at least one particulate material and to methods for making and using the compositions when mixing or preparing fracturing fluids, drilling fluids, completion fluids, production fluids and in other fluids used in oil and gas drilling, completion, production and stimulation operations. In formulations including hydratable polymers, the compositions also improves hydration properties of the hydratable polymer.
More particularly, the present invention relates to oil based slurry compositions having decreased particulate material settling rates and to formulations including the composition and at least one particular material, where the oil based slurry composition includes a hydrocarbon base fluid and an effective amount of a polymeric suspension agent sufficient to decrease particulate material settling rates and/or to improve hydration of hydratable polymers. The present invention also relates to methods for making and for using the compositions of this invention when mixing or preparing fracturing fluids, drilling fluids, completion fluids, production fluids and in other fluids used in oil and gas drilling, completion, production and stimulation operations.
2. Description of the Related Art
Delivery of particulate chemicals has been challenging in the oil and gas industry. The use of concentrated slurries of additives for water based fracturing fluids have serious problems relating to solid chemical additive transport in field applications. Settling of solid additive(s) during storage has been and continues to be problem requiring reblending prior to use. These problems have also been observed with commercial concentrate slurries of guar and guar derivatives, Xanthan and Xanthan derivatives, hydroxy-ethyl cellulose (HEC) and HEC derivatives or other polysaccharide polymers in hydrocarbon carriers.
The preparation of these slurry concentrates in field requires high shearing energies to disperse the hydrocarbon and the polymer before use in the hydration process to make linear gels. Preparing polymer slurries containing select surfactant(s) with high shear energy also facilitates water wetting of the polymer, which allows for rapid polymer hydration rate and viscosity development. Similar water wetting properties requiring high shear have also been observed with oil based concentrated slurry suspensions of borate crosslinkers for water based fracturing fluids such as mixtures of ulexite, calcined colemanite, and other additives.
Moreover, suspension compositions of other sold materials such as micronized salt, bentonite, silica flower, starches and other finely ground particulate materials have shown utility in oil and gas field and other industrial processes mention in this discussion.
Settling of the dispersion, as described above increases with temperature, especially when the temperature is higher than 80° F.
Historically, particle settling has mainly been addressed by using different amounts of organophillic clays, polar activators and dispersing surfactants in oil based concentrated slurries. These additives were found to improve suspension and avoid settling of the particles blended in the hydrocarbon base (e.g. diesel, mineral oil or similar hydrocarbons) for application in water based fracturing fluids.
In water based suspension, settling has been address by utilizing polymers that viscosify water or have unique suspension properties. These water viscosity modifier polymers include Xanthan gum or other polysaccharides like carboxymethylhydroxyethyl cellulose, guar gum or the like. This procedure was first introduced by Halliburton and has been and continues to be used by B J, Shlumberger, Weatherford, Rhodia, Economy Polymers among others. See, e.g., U.S. Pat. Nos. 4,312,675; and 4,828,034, incorporated herein by reference.
Thus, there is a need in the art for an anti-settling additive and compositions and formulation including the anti-settling additive that reduce settling in fracturing fluid, especially at temperature higher than 80° F.